Time-limit relay.



D. L. LINDQUIST & D. C. LARSON.

TIME LIMIT RELAY,

APPLICATION FILED JULY 7.1914.

1 ,288 62@ Patented Dec. 24, 1918.

2 SHEETS-SHEET 1.

H A 6, WITNESSES: INVENTOHS, yaw-1M4 W ATTOR V Patented Dec. 24, 1918.

2 SHEETS-SHEET 2.

D. L. LINDQUIST 62 D. C. LARSON.

TIME LIMIT RELAY.

APPLICATION FILED lULY 7. 1914.

wxww QRH IIIIL wb m k NM UNITED STATES PATENT OFFICE.

DAVID L. LINDQUIST AND DAVID C. LARSON, OF YONKERS, NEW YORK, ASSIGNORS TO OTIS ELEVATOR COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

TIME-LIMIT RELAY.

Specification of Letters Patent.

Application filed July 7, 1914. Serial No. 849,448.

To all whom it may concern:

Be it known that we, DAVID L. LIND UIs'r, a subject of the King of Sweden, and DAVID C. LARSON, a citizen of the United States, both residing in Yonkers, county of VVestchester, and State of New York, have invented a new and useful Improvement 1n Time-Limit Relays, of which the following is a specification.

Our invention relates to time limit relays, and has for an object the provision of a simple, practical and eflicient circuit controlling device which may have a general application, but which is particularly adapted automatically to protect an electric motor or other apparatus from damage caused by long continued overload or an abnormally heavy current flow.

The accompanying drawings illustrate a preferred embodiment of our invention, in j which Figure l is an elevation View of the device showing its application to an electric motor; Fig. 2 is a side elevation view of the device in part section; Figs. 3 and 4 are detail views in elevation and side section, respectively, of the relay contact when the same is in its normal position; Figs. 5 and 6 are detail views similar to Figs. 3 and 4, respectively, and showing the relay contact in its operated position.

Like reference characters denote similar parts in all of the figures.

Referring to the drawings, it will be seen that the device comprises a cast iron base 1 which is provided with lugs 2- -2, by means of which the same may be secured to a wall or switchboard or other suitable place. The upper part of the base forms a magnet frame 3 which incloses a solenoid 4, comprising a stationary adjustable core 5, and a movable core 6. The upper end of the core 6 is preferably tapered as shown, while the adjacent end of the core 5'contains a corresponding tapered recess. A screw-threaded rod 7 is secured to the core 6 by means of an eye 8 and pin 9, and this rod carries upon it a diamond shaped cam member 10 which may be adjusted upon the rod 7 and locked in place by means of the nuts 11. The lower end of the rod 7 is secured to a dashpot piston 12 by means of a pin 13. The piston 12 fits snugly into a dashpot 13 which normally rests upon a shelf 26 and is preferably filled with a light grade of 011, whose consistency is substantially unaffected by variations in temperature. The back of the dashpot is provided with a boss in which are two parallel grooves 15, 15, whlch embrace a pair ofslides 16 formed on the base 1, the construction being such that the dashpot may be moved bodily upon the slides 16, 16, in a vertical direction. Partially surrounding the dashpot are a number of are shaped removable rings 17, 17, which are for the purpose of weighting the dashpot to any desiredamount by addmg ortaklng away one or more of the rings. A by-pass or port 18 extends from the top to the bottom of the dashpot cylinder and permits the oil therein to be displaced upon a movement of the piston, the rate of displacement being controlled by means of a throttling screw 19 which may be adjusted to restrict the ort 18 to any degree desired. The cover 20 of the dashpot is concave and extends a considerable distance within the dashpot cylinder. The adjacent parts of the cover and piston are similarly shaped so that the resistance ofiered by the oil to the upward movement of the dashpot piston, gradually increases as the piston rises in the cylinder. A bracket 21 is secured to the base 1 above the dashpot, and this bracket is provided with a screw threaded boss 22 upon which is an adjustable nut 23. A compression spring 24 bears against the nut 23 and a nut 25 on the rod 7 and the same tends to maintain the rod 7 and dashpot piston 12 intheir downward position against the pull of the magnet 4. A cover 42 completely incloses and protects the Working parts of the device.

The contactdevice that cooperates with the cam member 10 is shown in detail in Figs. 3, 4, 5 and 6, and comprises an insulated block 27 which is secured to the base 1. The contact comprises a strip 28 of spring bronze or other suitable metal which is bent back .on itself and one end is provided with an insulated roller 29 which bears against the cam member 10. The other end of the spring contact 28 is bifurcated so as to form' two contacts 30 and 31 which form between them a rectangular groove 34 in which the spring contact 28 may slide. The latter also is in sliding engagement Patented Dec. 24, 1918.

with an adjustable block 36 containing a groove 35 in which the spring contact lies. A stop fpin 37 is adapted to limit the movement o the springcontact in one direction.

Integral with the arm of the spring contact 1 their normal position as shown in Figs. 3

and 4, and the cam member 10 to be slowly moved upwardly. As the roller 29 rides upon the inclined upper part of the cam, the spring contact 28 will be compressed until finally the peak of the cam passes beyond the roller. As soon as this takes'place, the roller at once runs down the lower inclined part of the cam, carrying with it the spring contact, and the latter assumes the position shown in Figs. 5 and 6. By this operation the bifurcated ends of the spring contact 30 and 31 are quickly snapped out of engagement with thestationary contacts 32 and 33, respectively, and take up a position on the insulated block 40 as shown in Figs. 5 and 6, so that any circuit that previously included the contacts 30, 31, 32 and 33 is immediately interrupted. Should the cam member 10 be moved downwardly, the roller 29' rides upon the lower inclined part of the cam, and as soon as the peak of the cam has passed away from the roller the latter immediately runs up the upper in-" clined part of the cam and the contact spring is snapped back into its original position as shown in Figs. 3 and 4. By reasonof this construction, we are enabledto effect a substantially instantaneous make-andbreak of the circuit controlled by the contact spring 28 regardless of the speed with which the cam may be moved. The spring contact will operate the instant the peak of the cam moves away from the roller 29 and the speed with which it will move depends largely upon the inclination of the cam faces and the tension to which the spring contact is subjected, and if these parts are constructed in substantially the same proportion as shown in the drawings, the action of the spring contact will be to allpractical purposes instantaneous, which of course is most desirable, in that it prevents the formation of an arcv as the contacts pass out of electrical engagement with each other.

When the device is used to protect a motor, we prefer so to arrange the parts thati after the circuit is once opened by the upward movement of the cam 10 a subsequent downward movement of the cam will not return the contact spring to closed circuit position, but rather that this spring contact must be returned by hand. In order to effect this result we provide the stop pin 39,

which automatically falls into position in front of the member 38 (see Figs. 4 and 5) when the spring contact is moved to open circuit position, and thus prevents the automatic return of the latter. Upon pulling out the milled head of the stop pin 39, the spring contact may be returned to closed circuit position by hand.

Referrin once more to Figs. 1 and 2, we will descri e the operation of the device when used to protect an electric motor. In this case the winding of the magnet 4 is of low resistance and is connected .in series with the armature circuit of a motor 42. A main line switch 41 controls the motor circuit, and the operating or holding magnet of this switch is connected in series with the contacts of the relay across the line. If the motor be operating at normal load, the magnet core 6 and connected cam member 10 will not be raised against the action of the compression spring 24. If, however, the motor should be subjected to excessive current flow, the magnet 4 becomes powerful enough to overcome the spring 24 and the cam 10 is carried upwardly to effect the openin of the relay contacts as already describe The opening of these contacts interrupts the holding circuit of the switch 41 and the latter opens the line circuit and cuts off the current to the motor and all the parts of the device with the exception of the spring contact 28 return to normal posltlon.

Thus far, nothing has been sa1d descriptive of the time limiting feature of the relay. This feature of the invention is most imrtant and resides in the novel arrangement of the dashpot.

As is well known, it is permissible, and under certain conditions desirable to permit excessive current to flow to a motor for a limited time, the strength of this current being such that if the same were allowed to flow for any considerable length of time the motor windings might be damaged. The usual type ofoverload circuit breaker does not permit of this condition, since it 1s set to operate at a predetermined overload and will open the motor circuit immediately this overload condition is reached. With the device herein disclosed the electric motor is permitted to withstand a certain overload for a predetermined length of time and at the expiration of that time the motor circuit is at once opened. In case of an unusually heavy overload or a short circuit the main line circuit to the motor is immediately opened. The manner in which we effect this result is as follows: Assume that the various parts of the device are in the position shown in Fig. 1, and the motor 42 becomes moderately overloaded. The core 6 of the relay tends quickly to raise the cam member 10, but this movement is-opposed by the spring 24 and the retarding action of the dashpot opening of the motor circuit. Since the retarding action of the dashpot may be controlled by restricting the by-pass or port 18, the time interval between the initial movement of the magnet core and the time at which the high part of the cam passes beyond the roller 29 maybe accurately deter-' mined so as to effect the desired results.

It will be observed that the upward movement of the dashpot piston tends bodily to carry the dashpot with it, but when the overload on the motor is moderate this tendency is successfully resisted by the weight of the dashpot assisted by the Weighted rings 17, 17, and the dashpot is not moved. If, however, the overload on the motoris excessive or a short circuit should exist, the upward pull'on themagnet core 6 is sufficiently powerful to'raise both piston and dashpot cylinder as a unit, with the result that the function of the dashpot becomes m'l, and the spring switch is immediately opened so as to cut off the motor circuit.

Under some conditions it is desirable that the upward movement of the magnet core and connected parts shall be at a constant slow speed throughout its entire stroke. In order to attain this result, the dashpot is so arranged that its retarding action increases as the piston rises which just compensates for the increased pull of the magnet core as the latter moves upwardly and the resist ance of itsm'agnetic circuit decreases. The variable retarding action of the dashpot is due to the increasing choking of the fluid between the dashpot piston and the adjacent portion of the dashpot cover as the piston moves upwardly. The coactingends of the.

magnet cores 6 and 5 are tapered in order that the variable pull of the core 6 as it moves upwardly may be more nearly uniform than if .the adjacent ends of the cores were made flat as is the usual practice.

Our invention may be used to advantage for controllin any desired circuit, and 1n case the time-lmiitin feature is not desired,

the dashpot may be ispensed with. If it is.

desired that the relay shall directly control a circuit carrying a substantial current rather than employ an intermediate device,

such as the switch 41 of Fig. 1, it becomes necessary merely to increase the current carrying capacity of the spring contact. The device is simple,-and requires but few parts. All troublesome triggers, latches and trips are dispensed with, and the result is a most practical and efficient mechanism admirably suited for a great many different purposes.

While we have disclosed herewith a 'preferred embodiment of our invention, we desire not to be limited to the precise construction and arrangement of parts herein shown and disclosed, since it is obvious that one skilled in the art could readily suggest changes Without departingfrom the spirit and scope of the invention.

What we claim is Y 1. An eleetro-responsive device comprising a solenoid and movable core, a fluid dashpot connected with the core, and means" for effecting a variable retarding action of the dashpot whereby the solenoid core is constrained to move at a uniform rate of speed throughout its range of movement.

2. A relay comprising a solenoid and movable core, a retarding device connected with the core, ,means for effecting a variable action of said retarding device whereby the solenoid core is constrained to move at a uniform rate of speed and a quick-acting circuit-controlling device operated by said core. w

' I: 3. A relay comprising a solenoid and movable core, a retarding device connected with the core, means for efi'ecting a variable action of said retarding device whereby. the solenoid ccre is constrained to move at a uniform rate of speed, a switch controlled,

' by said core, and means for efiecting a quick action of said switch regardless of the rate bf movement of the said core.

4. A time limit relay comprising .a s0- lenoid, a movable core therein, contacts controlled by the core, a fluid dashpot retarding device for the core, and means for preventing bodily movement of said dashpot except upon excessive current flow in said solenoid.

5. A time limit relay comprising a solenoid, a core movable therein, contacts controlled by the c'ore, a piston connected with the core, a dashpot cylinder for the piston, and means for preventin a bodily movement of both piston a'n' upon a predetermined excess current flow in the solenoid.

6. A time limit relay comprising a so lenoid, a core movable therein, contacts con cylinder except held against movement but permitted bodily to move upon abnormal current flow in the solenoid.

8; A time limit relay comprising a solenoid, a core movable therein, contacts controlled by the core,-a dashpot adapted bodily to move, a piston in the dashpot connected to the core, and removable Weights associated with the dashpot for normally maintaining the latter against movement while permitting the dashpot bodily to move upon abnormal current flow in said solenoid.

9. A time limit relay comprising a solenoid, a core movable therein and connected to a piston, a dashpot for retarding the piston and core, slides upon which the dashpot is adapted to travel means normally for holding the dashpot against movement as the piston is moved by the core but permitting the dashpot bodily to move upon an abnormal current flow in the solenoid, and a quickacting switch controlled by the core.

10. A time limit relay comprising a solenoid, a core movable therein and connected to a piston, a dashpot for retarding the piston and core,slides upon which the dashpot is adapted to travel, means comprising a plurality of removable Weighted rings associated with the dashpot normally for holding the dashpot against movement as the piston is moved by the core but permitting the dashpot bodily to move upon an abnormal current flow in the solenoid, and a quick acting switch controlled by the core.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

DAVID L. LINDQUIST.

Witnesses: 1

L. H. CAMPBELL, JAMES G. BETHELL. 4

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

DAVID C. LARSON.

Witnesses:

WALTER C. STRANG, ERNEST L. GALE, Jr. 

